Evaluation of the effects of masons’ trowel handle shape on electrical activity of the forearm and upper arm muscles

Abstract

Introdution and Objetives The tool handles are usually used for holding, moving, transmiting power, generating torque, and moving objects. Hand tools design, especially tool handles, is the most important part of hand tools to ergonomists. Also that is a complex task in which design requires attention to the functionality, quality and reliability of hand tools, but must also take into account the expectations and perceptions of users.The handle shape of the hand tool as an important part of the handle can play an important role in mental comfort, work performance and the contact area between the palms and handles for better distribution of pressure and lower unit pressure on the hands and muscles when working with hand tools.With this in mind, Diant et al. (2015) designed five handle shapes of masons’ trowels in accordance with the suggestions in literature with different pattern of grip, which performed the subjective evaluation of this tool, but the objective evaluation (EMG) did not. Therefore, according to th mentioned background, the purpose of this study was to evaluate the shape of the designed handles on the electrical activity of the forearm and arm muscles. Materials and Methods 18 male students of Tabriz University of Medical Sciences with an age range of 21-29 (mean age: 26) participated in this study. Participation in the study was voluntary and the consent of each individual has been taken at the beginning of the study through the informed consent form. The inclusion criteria for the study included a lack of pain or a history of musculoskeletal complications and damage, especially in the arm and hand region, which was self-reported. In this study, five different handles were designed by different design software, as well as a traditional trowel that was used repeatedly by masons in construction work. In this experiment, the working conditions were the same for all participants in the study. Each test session lasted about 2 hours and was carried out at specific time (between 10:00 and 12:00 in the morning) to prevent the bias among participants. The electrical activity level of the forearm and armmuscles, expressed as a percentage of maximal voluntary contraction, was evaluated by an electromyograph. Finally, the statistical analysis was performed by SPSS software (version 23), taking into account the significance level of P <0.05. Findings The overall test results showed that the shape of the handle showed a significant effect on muscle activity of the FDS, BB, ECU muscles, but no significant effect was found for the PT muscle. The results also showed that the level of electrical activity of the arm muscle was generally lower than the other three muscle, While the highest level of electrical activity was recorded for the ECU muscle. The results also showed that the anthropometric dimensions of the hand had no significant effect on the electrical activity of the muscles. Conclusion The findings and recommendations for tool design in this study were based on the shape of the handle as one of the design considerations in hand tools design. Obviously, consideration of other design features (such as texture, cross-section, etc.) may be required in future studies to fully confirm the overall impact of proposed projects. In addition, the study participants provided a fairly short time to evaluate each of the prototypes in the laboratory environment, while the actual working conditions could be different from the results of the study, and so when using this finding Should be considered.